Optimize substr() edge-case conditions

Author: dstogov

ext/standard/string.c

@@ -2415,52 +2415,53 @@ PHP_FUNCTION(substr)
 		Z_PARAM_LONG(l)
 	ZEND_PARSE_PARAMETERS_END();
 
-	if (argc > 2) {
-		if ((l < 0 && (size_t)(-l) > ZSTR_LEN(str))) {
-			RETURN_FALSE;
-		} else if (l > (zend_long)ZSTR_LEN(str)) {
-			l = ZSTR_LEN(str);
-		}
-	} else {
-		l = ZSTR_LEN(str);
-	}
-
 	if (f > (zend_long)ZSTR_LEN(str)) {
 		RETURN_FALSE;
-	} else if (f < 0 && (size_t)-f > ZSTR_LEN(str)) {
-		f = 0;
-	}
-
-	if (l < 0 && (l + (zend_long)ZSTR_LEN(str) - f) < 0) {
-		RETURN_FALSE;
-	}
-
-	/* if "from" position is negative, count start position from the end
-	 * of the string
-	 */
-	if (f < 0) {
-		f = (zend_long)ZSTR_LEN(str) + f;
-		if (f < 0) {
+	} else if (f < 0) {
+		/* if "from" position is negative, count start position from the end
+		 * of the string
+		 */
+		if ((size_t)-f > ZSTR_LEN(str)) {
 			f = 0;
+		} else {
+			f = (zend_long)ZSTR_LEN(str) + f;
 		}
-	}
-
-	/* if "length" position is negative, set it to the length
-	 * needed to stop that many chars from the end of the string
-	 */
-	if (l < 0) {
-		l = ((zend_long)ZSTR_LEN(str) - f) + l;
+		if (argc > 2) {
+			if (l < 0) {
+				/* if "length" position is negative, set it to the length
+				 * needed to stop that many chars from the end of the string
+				 */
+				if ((size_t)(-l) > ZSTR_LEN(str) - (size_t)f) {
+					if ((size_t)(-l) > ZSTR_LEN(str)) {
+						RETURN_FALSE;
+					} else {
+						l = 0;
+					}
+				} else {
+					l = (zend_long)ZSTR_LEN(str) - f + l;
+				}
+			} else if ((size_t)l > ZSTR_LEN(str) - (size_t)f) {
+				goto truncate_len;
+			}
+		} else {
+			goto truncate_len;
+		}
+	} else if (argc > 2) {
 		if (l < 0) {
-			l = 0;
+			/* if "length" position is negative, set it to the length
+			 * needed to stop that many chars from the end of the string
+			 */
+			if ((size_t)(-l) > ZSTR_LEN(str) - (size_t)f) {
+				RETURN_FALSE;
+			} else {
+				l = (zend_long)ZSTR_LEN(str) - f + l;
+			}
+		} else if ((size_t)l > ZSTR_LEN(str) - (size_t)f) {
+			goto truncate_len;
 		}
-	}
-
-	if (f > (zend_long)ZSTR_LEN(str)) {
-		RETURN_FALSE;
-	}
-
-	if ((size_t)l > ZSTR_LEN(str) - (size_t)f) {
-		l = ZSTR_LEN(str) - f;
+	} else {
+truncate_len:
+		l = (zend_long)ZSTR_LEN(str) - f;
 	}
 
 	if (l == 0) {